Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 18, 2000
Publication Date: December 1, 2000
Citation: Tillman, P.G., Mulrooney, J.E. 2000. Effect of selected insecticides on natural enemies, Coleomegilla maculata and Hippodamia convergens (Col.:Coc.), and Geocoris punticipes (Hem.:Lyg.), and Bracon mellitor, Cardiochiles nigriceps, Cotesia marginiventris...cotton. Journal of Economic Entomology. 93(6):1638-1643. Interpretive Summary: The boll weevil, the corn earworm, the beet armyworm, cotton aphids, and the tobacco budworm are important insect pests of cotton and other agricultural crops, and infestations of the pests can significantly reduce yield. I am actively looking for methods to minimize damage by these insects while reducing the use of insecticides. The wasps, Bracon mellitor, Cardiochiles nigriceps, and Cotesia marginiventris, and the predators, Coleomegilla maculata, Geocoris punctipes, and Hippodamia convergens, are predominant natural enemies of these pests. The purpose of this study was to determine the toxicity of three insecticides, the experimental compound numbered S-1812, Tracer, and Karate, to these natural enemies. Our results showed that Karate generally was highly toxic to natural enemies. Tracer exhibited marginal to excellent selectivity, but was highly toxic to each wasp species and G. punctipes in some tests. S-1812 exhibited good to excellent selectivity to the natural enemies. In conclusion, Tracer and S-1812 should be excellent tools in conserving valuable natural enemies.
Technical Abstract: We evaluated the toxicity of three insecticides (lambda cyhalothrin, spinosad, and S-1812) on the natural enemies Bracon mellitor Cardiochiles nigriceps, Coleomegilla maculata, Cotesia marginiventris, Geocoris punctipes, and Hippodamia convergens, in topical, residual, and field assays. Lambda cyhalothrin exhibited the greatest toxicity to the natural enemies. Spinosad exhibited marginal to excellent selectivity, but was highly toxic to each parasitoid species and G. punctipes in topical toxicity tests and to B. mellitor in residual tests. Spinosad generally did not affect the number of G. punctipes, H. convergens, and C. maculata in the field except for one day after the second application for G. punctipes. S-1812 exhibited good to excellent selectivity to the natural enemies. Some reduction of G. punctipes occurred for only a short period of time after the first and second application of this insecticide in the field. H. convergens and C. maculata were affected very little by S-1812.